Gas injection valve

ABSTRACT

A gas injection valve designed for long-term storage of liquefied carbon dioxide, adapted to minimize the permeation of carbon gas through a seal ring even if used for a long time, thus solving the problems including an increase in injection concentration of the contents and a decrease in the number of times of spraying. Particularly, it is arranged that a seal ring closely contacts the three surfaces of a seal ring holding groove holding the seal ring, and the outer peripheral surface of a valve pin, whereby the gas permeation area of the seal ring is reduced to a half or less of the conventional valve. Further, the seal ring is made of an elastic material whose carbon dioxide gas permeability is low, thereby greatly reducing the amount of gas permeation through the seal ring.

TECHNICAL FIELD

The present invention relates to a gas injection valve for injectingcontents filled in a gas container by using liquefied carbon dioxide gasas a propellant, and to a gas injection valve in which improvements aremade on the leakage and permeation of carbon dioxide gas at sealingportions during storage and in long-term use.

BACKGROUND ART

Conventionally, there have been used systems in which contents such asmedical agents are filled into a gas container along with a gas, and thecontents are injected out of a gas injection valve fixed to andinstalled on an opening of the gas container under the gas pressure.Injection systems of this type have conventionally usedchlorofluorocarbons as the propellant, whereas ones usingchlorofluorocarbon substitutes are now becoming available in view ofinfluence on the ozone layer.

Nevertheless, while they have no effect on the ozone layer, thesechlorofluorocarbon substitutes have a significant impact on globalwarming. Various measures against this, similar to those againstchlorofluorocarbons, are thus expected to be taken in the future. Inthese days, it has thus been contemplated to use carbon dioxide gas,nitrogen gas, and inactive gases including helium, neon, and krypton,which have smaller impacts on global environment and are safe for eventhe human body, as the propellants of the injection systems.

By the way, when such gases are used as the propellants of the injectionsystems, it is desirable that the gases be liquefied like the existingchlorofluorocarbons for the sake of compatibility with the medicalagents and miniaturization of the gas containers. With liquefied carbondioxide gas, for example, the vapor pressure at 20° C. is 58.4 kgf/cm².It is preferred that other gases be also highly compressed or liquefiedfor improved volumetric efficiency. In particular, they are desirablyused at pressures not lower than 50 kgf/cm².

For an injection valve using such a high-pressure gas as its propellant,one such as described in Japanese Patent Laid-Open Publication No. Hei11-267557 has been devised heretofore.

As shown in FIGS. 6 and 8, this gas injection valve has a valve case 120which is fixed to the opening of a gas container 110. A valve pin 130for opening and closing a channel opening 190 by a push-in operationfrom exterior of the gas container 110 is supported by the valve case120 so as to be capable of moving back and forth. The valve pin 130comprises an ordinary part 130a which is in tight contact with a secondseal ring 170 arranged in the valve case 120, and a piston part 130 bwhich lies below this ordinary part 130 a. In a steady state where thevalve pin 130 is not pushed in, a first seal ring 230 and a third sealring 240 of the piston part 130 b each make tight contact with thesurface of a cylinder hole 150 in the valve case 120, whereby thechannel opening 190 mentioned above is kept in a blocked state.

Since this gas injection valve has the foregoing configuration, thethird seal ring 240 is in tight contact with the surface of the cylinderhole 150 in the valve case 120 when the extremity of the valve pin 130is pushed in from exterior of the gas container 110. Meanwhile, thefirst seal ring 23 moves to a tapered surface 270 lying below thecylinder hole 150. This establishes communication between the interiorof the gas container 110 and the channel opening 190, and the contentsof the gas container 110 are then injected out along with the gas.

In the conventional gas injection valve described above, however, thesecond seal ring 170 intended to prevent the gas inside the gascontainer 110 from leaking outside causes the phenomenon that arelatively large amount of high-pressure gas permeates the second sealring 170 to dissipate outside as shown in FIG. 7.

In particular, when liquefied carbon dioxide gas having a gaspermeability 15 times or more that of nitrogen gas is used as thepropellant, the amount of permeation of the gas through the second sealring 170 becomes large during long-term storage and long-term use. Forexample, if the seal ring 170 is made of a NBR (nitrile rubber) having arubber hardness of 60 degrees, which is a typical sealing material, anda gas container having a capacity of 10 cc is filled 60% with liquefiedcarbon dioxide gas at 20° C., then 40% or more of the carbon dioxide gascan dissipate outside during one year of storage at room temperature. Asa result, there occur such impractical defects that the contents to beinjected from the gas container increase in concentration excessively,and that a predetermined number of injections can no longer be secured.

In general, the amount of permeation of gas is in proportion to the areaof the object to be permeated on which the gas pressure is loaded. Inthe foregoing phenomenon, the gas pressure is loaded all over thesurface of the second seal ring 170 facing toward the interior of thegas container 110. This shows that a large amount of gas permeates thesecond seal ring 170.

Then, focusing attention on the design of the annular groove foraccommodating a seal ring and the material of the seal ring, the presentinvention is to provide a gas injection valve of sufficientpracticability in which the amount of permeation of carbon dioxide gasthrough the seal ring is made extremely small so that the concentrationof the contents to be injected is stabilized and a predetermined numberof injections is secured.

DISCLOSURE OF THE INVENTION

As means for solving the foregoing problem, a gas injection valve of thepresent invention according to claim 1 is a gas injection valve inwhich: a valve pin is held by a valve case fixed to an opening of aliquefied carbon dioxide gas container, so as to be capable of movingback and forth; a seal ring for establishing sealing between the valvecase and the valve pin is attached to an inner periphery of this valvecase; and the valve pin is provided with a gas channel for establishingcommunication between exterior of the gas container and a part of thegas container lying inner than the seal ring in the valve case when thepin is pushed in from exterior. An annular space for accommodating theseal ring is formed so that the seal ring is in tight contact with allof three sides, or a bottom and both sides, of a holding groove of thevalve case for holding the seal ring, and an outer periphery of thevalve pin. The seal ring is made of an elastic material having a rubberhardness of 65 degrees or higher.

In this invention, the seal ring is in tight contact with all of thebottom and both sides of the holding groove for holding the seal ringand the outer periphery of the valve pin. This reduces the load of thehigh gas pressure of the liquefied carbon dioxide gas to or below a halfof that on the surface of a seal ring that faces toward the interior ofthe gas container. The amount of permeation of the gas decreasesaccordingly.

Moreover, the gas permeability of the seal ring differs considerablywith a material used, and varies with rubber hardness as well. While itis desirable to use a seal ring made of a material having gaspermeability as low as possible, there has not been known any particularmaterial or rubber hardness setting suitable for liquefied carbondioxide gas, which were thus determined by carbon dioxide gas permeationexperiments. As a result, it was found that elastic materials havingrubber hardnesses of 65 degrees or higher, i.e., in particular, HNBR(hydrogenated nitrile rubber), IIR (butyl rubber), CSM (chlorosulfonatedpolyethylene), CO (epichlorohydrin rubber), U (urethane rubber), and T(polysulfide rubber), have low permeability to carbon oxide gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a first embodiment of the gasinjection valve of the present invention;

FIG. 2 is a detailed partial view of the embodiment;

FIG. 3 is a sectional view showing the embodiment;

FIG. 4 is a sectional view showing a second embodiment of the gasinjection valve of the present invention;

FIG. 5 is a sectional view showing a third embodiment of the gasinjection valve of the present invention;

FIG. 6 is a sectional view showing a gas injection valve of theconventional technique;

FIG. 7 is a detailed partial view of the same; and

FIG. 8 is a sectional view showing the gas injection valve of theconventional technique.

The individual numerals have the following meanings:

-   -   10 . . . gas injection valve    -   11 . . . valve case    -   11 a . . . upper part    -   11 b . . . lower part    -   12 . . . valve pin    -   13 . . . gas channel hole    -   13 a . . . axial hole    -   13 b . . . orifice hole    -   14 . . . stopper flange    -   16 . . . guide hole    -   17 . . . seal ring    -   18 . . . seal ring holding groove    -   18 a . . . upper side    -   18 b . . . lower side    -   18 c . . . bottom    -   30 . . . gas container    -   31 . . . gas container opening    -   40 . . . nozzle button    -   50 . . . lower block    -   51 . . . upper block

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a gas injection valve to be provided by the presentinvention will be described in conjunction with specific embodimentswith reference to the drawings.

Initially, a first embodiment of the gas injection valve of the presentinvention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows an injection system using a gas injection valve 10according to the present invention. In this injection system, the gasinjection valve is hermetically attached to a gas container 30 which isfilled with liquefied carbon dioxide gas and contents such as medicalagents.

The gas injection valve 10 comprises a valve case 11 which is fixedairtightly to a gas container opening 31 of the gas container 30 bycaulking, and a valve pin 12 which is held by this valve case 11 so asto be capable of moving back and forth. A nozzle button 40 having both anozzle function and a push button function is fitted and fixed to theextremity of the valve pin 12 which protrudes upward from the valve case11.

A guide hole 16 for the valve pin 12 to be fitted into is formed in theaxial central area of the valve case 11 along the axial direction. Aseal ring holding groove 18 having a U-shaped section, which openstoward the axial center, is formed generally in the axial centralposition of this guide hole 16. A seal ring 17 made of an elasticmaterial is held inside the seal ring holding groove 18.

Then, this seal ring holding groove 18 is set so that the seal ring 17makes tight contact with all of its three sides, or a bottom 18 c, anupper side 18 a, and a lower side 18 b, and the outer periphery of thevalve pin 12.

Meanwhile, a gas channel hole 13 for establishing communication betweenthe top end and the outer periphery of the valve pin 12 at apredetermined distance away from the top end axially is formed in theextremity side of this valve pin 12 protruding upward from the valvecase 11. Specifically, this gas channel hole 13 is made of an axial hole13 a which is formed along the axial direction from the top end of thevalve pin 12, and an orifice hole 13 b which is formed along the radialdirection to establish communication between the bottom of this axialhole 13 a and the outer periphery of the valve pin 12. Then, thisorifice hole 13 b is set so that it opens to where closer to theexterior of the gas container 30 than the seal ring 17 when the valvepin 12 is in the lifted position, and opens to where closer to theinterior of the gas container 30 than the seal ring 17 when the valvepin 12 is pushed in from exterior.

A stopper flange 14 is formed integrally on the lower part of the valvepine 12 which lies inside the gas container 30. This stopper flange 14comes into contact with the underside of the valve case 11 to restrainthe lifting displacement of the valve pin 12.

Since this gas injection valve 10 has the foregoing configuration, thevalve pin 12 is impelled to the topmost position by the gas pressureinside the gas container 30 and the orifice hole 13 b lies above theseal ring 17 while the nozzle button 40 is not pushed in. Here, the gaschannel hole 13 is thus out of communication with the interior of thegas container 30.

Then, when the nozzle button 40 is pushed in from this state, the valvepin 12 lowers to a position closer to the interior of the gas container30 than the seal ring 17. The gas inside the gas container 30 isinjected outside through the gas channel hole 13 and the hole in thenozzle button 40 along with the contents.

Concerning the gas dissipation from the guide hole 16 when this gasinjection valve 10 is not in use such as during storage, the seal ring17 is in tight contact with all the three sides, or the bottom 18 c, theupper side 18 a, and the lower side 18 b, of the seal ring holdinggroove 18 for holding the seal ring 17 and the outer periphery of thevalve pin 12. This precludes the high-pressure carbon dioxide gas havinghigh gas permeability from being loaded all over the surface of the sealring 17 facing toward the interior of the gas container 30 as in theconventional technique, and the loaded area decreases to a half or less.Since the amount of permeation of the gas is in proportion to the areaof the object to be permeated on which the gas pressure is loaded, it ispossible to reduce the amount of permeation of the gas accordingly withreliability.

Moreover, from carbon dioxide gas permeation experiments, elasticmaterials having low gas permeability were determined as the material ofthis seal ring 17. As a result, HNBR (hydrogenated nitrile rubber), IIR(butyl rubber), CSM (chlorosulfonated polyethylene), CO (epichlorohydrinrubber), U (urethane rubber), and T (polysulfide rubber), which areelastic materials having low permeability to carbon dioxide gas andrubber hardnesses of 65 degrees or higher, could be used to reduce thegas permeability of the seal ring 17 with reliability.

Next, a second embodiment of the gas injection valve of the presentinvention shown in FIG. 4 will be described. Incidentally, the gasinjection valve 10 of this embodiment has the same basic configurationas that of the first embodiment shown in FIG. 1 except the valve case11. The same parts will thus be designated by identical numerals, andoverlapping description will be omitted.

The valve case 11 of this gas injection valve 10 is configured so that apart of the valve case 11 closer to the interior of the gas container 30than the lower side 18 b of the seal ring holding groove 18 is separatedinto a lower block 50. This lower block 50 is fixed airtightly bycaulking the bottom 11 b at the underside of the valve case 11. As inthe first embodiment, this precludes the high-pressure carbon dioxidegas from being loaded all over the surface of the seal ring 17 facingthe interior of the gas container 30. The loaded surface is a half orless as in the first embodiment, and it is possible to reduce the amountof permeation of the carbon dioxide gas accordingly with reliability.

Incidentally, in the second embodiment described above, in order to formthe seal ring holding groove 18, the part of the valve case 11 lyingcloser to the interior of the gas container 30 than the lower side 18 bof the seal ring holding groove 18 is separated into the lower block 50.This lower block 50 is then fixed airtightly by caulking the bottom 11 bat the underside of the valve case 11. On the other hand, as in a thirdembodiment shown in FIG. 5, a part of the valve case 11 lying closer tothe exterior of the gas container 30 than the upper side 18 a of theseal ring holding groove 18 may be separated into an upper block 51. Bycaulking the upper part 11 a at the topside of the valve case 11, thisupper block 51 can also be fixed airtightly to reduce the amount ofpermeation of the gas with reliability as in the first and secondembodiments.

INDUSTRIAL APPLICABILITY

As has been described above, the gas injection valves of the presentinvention provided by claims 1 to 7 are ones in which the seal ring isput into tight contact with all the three sides, or the bottom, upperside, and lower side, of the seal ring groove for holding the seal ringand the outer periphery of the valve pin. Consequently, even with thehigh-pressure carbon dioxide gas having high gas permeability as in theconventional technique, the gas pressure will not be loaded all over thesurface of the seal ring facing toward the interior of the gascontainer, and the loaded area decreases to a half or less. The amountof permeation of the gas can thus be reduced by half with reliability,allowing a significant improvement at low cost equivalent to in theconventional technique.

Then, even for the material of the seal ring, elastic materials havinglow gas permeability were determined through carbon dioxide gaspermeation experiments. As a result, HNBR (hydrogenated nitrile rubber),IIR (butyl rubber), CSM (chlorosulfonated polyethylene), CO(epichlorohydrin rubber), U (urethane rubber), and T (polysulfiderubber), having rubber hardnesses of 65 degrees or higher, are used toallow a further reduction in the amount of permeation of the carbondioxide gas through the seal ring. This also allows an improvement atlow cost equivalent to in the conventional technique.

Thus, according to the present invention, it is possible to make thepermeation of the carbon dioxide gas extremely small even when theliquefied carbon dioxide gas container is put to long-term storage andlong-term use. This provides the advantages that the concentration ofthe contents to be injected will not increase excessively, and that itis possible to resolve the problem of occurrence of such impracticaldefects that a predetermined number of injections cannot be secured.

1. A gas injection valve in which: a valve pin is held by a valve case fixed to an opening of a liquefied carbon dioxide gas container, so as to be capable of moving back and forth; a seal ring for establishing sealing between the valve case and the valve pin is attached to an inner periphery of this valve case; and the valve pin is provided with a gas channel for establishing communication between exterior of the gas container and a part of the gas container lying inner than the seal ring in the valve case when the pin is pushed in from exterior, wherein an annular space for accommodating the seal ring is formed so that the seal ring is in tight contact with all of three sides, or a bottom and both sides, of a holding groove of the valve case for holding the seal ring, and an outer periphery of the valve pin; and the seal ring is made of an elastic material having a rubber hardness of 65 degrees or higher.
 2. The gas injection valve according to claim 1, wherein the seal ring is made of HNBR (hydrogenated nitrile rubber) having a rubber hardness of 65 degrees or higher.
 3. The gas injection valve according to claim 1, wherein the seal ring is made of IIR (butyl rubber) having a rubber hardness of 65 degrees or higher.
 4. The gas injection valve according to claim 1, wherein the seal ring is made of CSM (chlorosulfonated polyethylene) having a rubber hardness of 65 degrees or higher.
 5. The gas injection valve according to claim 1, wherein the seal ring is made of CO (epichlorohydrin rubber) having a rubber hardness of 65 degrees or higher.
 6. The gas injection valve according to claim 1, wherein the seal ring is made of U (urethane rubber) having a rubber hardness of 65 degrees or higher.
 7. The gas injection valve according to claim 1, wherein the seal ring is made of T (polysulfide rubber) having a rubber hardness of 65 degrees or higher. 